I know that's what you're paying for, but I wonder what the marginal effects are. I.e. am I paying for a 100% renewable energy that otherwise would have been so

I know that's what you're paying for, but I wonder what the marginal effects are. I.e. am I paying for a 100% renewable energy that otherwise would have been sold to a customer not on a renewable plan? If I use more of the 100% renewable energy, does that increase the amount of non-renewable energy that must be generated for other people's consumption? I have no idea how grids work.